The instant invention relates generally to acoustic transducers used in non-destructive materials testing and underseas applications and more particularly to a transducer and reflector combination which stimulates a focused-arc transducer which produces a line-focus sound beam characteristic of focused-arc transducers.
It is well known in the art of acoustical non-destructive testing that it is desirable to use a sharply focused beam of energy. Many methods have been tried including various shaped transducers and other beam focusing methods such as with acoustic lenses and the like, but none was completely satisfactory for a sharply focused beam.
It has been discovered that the radiation from an annular or ring-shaped transducer, which emits a hollow substantially cylindrical beam of energy, may be effectively and sharply focused along a line having great depth of field emanating from the transducer. This line focus has many advantages over a normal point focus, which is at a certain distance from the focusing apparatus.
Producing an annular or ring-shaped transducers is difficult particularly because the very narrow annulus must be made of separate piezo-electric elements that are selected to be matched in output in order to define a good focus of radiated energy and to minimize the effects of differences in the resonant frequency. This limits the acoustic power that may be transmitted and tends to introduce extraneous reasonances in the transducer.
In view of this difficulty it is desirable to be able to simulate a focused arc-shaped transducer with a simple disc transducer and reflectors or or refractors that can operate at high powers and produce a sharp focus over a great depth of field.